Filamentous fungi have been shown to be excellent hosts for the production of a variety of proteins. Fungal strains such as Aspergillus, Trichoderma, Penicillium and Myceliophthora have been applied in the industrial production of a wide range of enzymes, since they can secrete large amounts of protein into the fermentation broth. The protein-secreting capacity of these fungi makes them preferred hosts for the targeted production of specific enzymes or enzyme mixtures. However, typically, these hosts secrete a mixture of many different enzymes, making the crude protein product undefined and requiring complex purification schemes for the desired protein. Even in cases where the gene encoding the target enzyme is over-expressed by genetic modification, the target enzyme will only constitute a minor part of the total secreted protein.
Hence, it is highly desirable to provide a fungal production system which is able to secrete high amounts of a specific enzyme without the presence of high levels of other proteins.
Such a production system would enable the production of a relatively pure enzyme and a simplified large scale purification of the desired enzyme. The produced enzyme can be used for different applications, e.g. for food and feed applications, in detergents and home care as well as in plant biomass hydrolysis (biofuels and chemicals), textile finishing and in paper and pulp industry.
WO 2010/107303 A2 describes the UV-induced mutagenesis of a Myceliophthora thermophila strain leading to isolates which produce low amounts of endogenous cellulase and proteases. Visser et al. (2011) Industrial Biotechnology 7(3): 214-223 disclose a Myceliophthora thermophila strain called LC (low-cellulase) strain which has lost almost all of its ability to produce cellulase.
Nevertheless, there is still a need for an efficient method for producing a recombinant polypeptide in filamentous fungi.